AIM: Although increased intraluminal pressure in the stomach due to gastric outlet obstruction or functional gastric motor dysfunction, including gastroparesis, may affect gastric mucosal integrity, the direct effect of mechanical pressure on gastric mucosal cells has not yet been fully investigated. The aims of this study were to determine whether exposure to transmural pressure would affect the proliferation of gastric mucosal cells and to elucidate the intracellular signaling pathways involved.METHODS: Cellular proliferation and DNA synthesis were evaluated in rat gastric epithelial cells exposed to high transmural pressures. The levels of activation of 3 MAP kinases, ERK, JNK, and p38, were assessed, and the induction of immediate early gene expression was examined. The activation of nuclear factor activator protein-1 (AP-1) was evaluated by an electrophoretic mobility shift assay.RESULTS: Exposure to high transmural pressure significantly increased DNA synthesis within 24 h, with the most marked increase observed after exposure to a pressure of 80 mmHg, and this increase was inhibited by the MEK1 inhibitor PD98059. Early activation of ERK kinase, but not of JNK or p38 kinase, was detected after pressure loading. Early induction of the c-fos and c-myc genes and activation of the AP-1 transcription factor were also demonstrated within 3 h of exposure to 80 mmHg of pressure.CONCLUSION: Gastric mucosal cell proliferation induced by exposure to high transmural pressure may be related to early activation of ERK, the induction of c-fos and c-myc, and the activation of AP-1.